THE  EFFECT  OF  TEMPERATURE  UPON  THE 
FULL  - EYED  RACE  OF  DROSOPHILA 


By 

ROSELLE  KARRER 

A.  B.  University  of  Illinois,  1921 


THESIS 

SUBMITTED  IN  PARTIAL  FULFILLMENT  OF  THE  REQUIREMENTS 
FOR  THE  DEGREE  OF  MASTER  OF  ARTS  IN  ZOOLOGY 
IN  THE  GRADUATE  SCHOOL  OF  THE  UNIVERSITY 
OF  ILLINOIS,  1922 


URBANA,  ILLINOIS 


i 


THE  GRADUATE  SCHOOL 


LIay 29 .192 


i HEREBY  RECOMMEND  THAT  THE  THESIS  PREPARED  UNDER  MY 
SUPERVISION  BY Roselle l_  Karrer 

ENTITLED — The  Effect  of  Temperature  upon  the  Full-6yed 
Race  of  Drosophila. 

BE  ACCEPTED  AS  FULFILLING  THIS  PART  OF  THE  REQUIREMENTS  FOR 
THE  DEGREE  OF  VaR ter  of  Arts, 


Recommendation  concurred  in* 


Committee 

on 

Final  Examination* 


Required  for  doctor’s  degree  but  not  for  master’s 


THE  EFFECT  OP  TEMPERATURE  UP OH  THE  PULL -EYED  RACE  OF  DROSOPHILA 


CONTENTS . 


I.  Introduction 

II.  Materials  and  Methods 

1)  Stock  used 
2}  Temperature  control 

3)  Technique 

4)  Sources  of  Error 

5)  Method  of  Tabulation 

III.  Results  of  Experiments 

IV.  Discussion 

1)  Comparison  of  counts  with  the  counts  obtained  by  Krafka 

2)  Comparison  of  temperature  effects  on  full  with  the 
temperature  effects  on  its  allelomorphs 

3)  Sexual  Dimorphism 

V.  Summary 

VI.  Bibliography 


Digitized  by  the  Internet  Archive 
in  2015 


https://archive.org/details/effectoftemperatOOkarr 


I.  Introduction. 

Seyster  and  Krafka  have  shown  that  the  effect  which  is 
produced  by  the  bar  gene  in  the  reduction  of  facet  number  from  full 
depends  upon  the  temperature.  At  the  same  constant  tempera.ture  the 
same  effect  is  produced  while  at  different  temperatures  the  amount 
of  change  in  number  of  facets  varies  inversely  with  the  temperature. 
ICrafka(l920)  studied  the  effects  of  temperature  upon  the  full -eyed 
race  at  15°  and  27° C . He  states  “The  counts  at  hand  show  that 
temperature  does  not  effect  facet  number  in  full  eye  to  a marked 
degree'.’  It  has  been  the  purpose  of  the  present  study  to  find 
whether  and  how  temperature  does  effect  facet  number  in  the  full- 
eyed  race  by  counting  a greater  number  of  flies  at  different  tem- 
perature intervals  than  given  by  Krafka.  The  result  of  the  study 
shows  that  facet  number  in  full  does  vary  with  the  temperature.  The 
effect  produced  per  degree  is  not  however  as  great  as  the  effect 
produced  in  the  bar  stocks. 

The  earlier  workers  of  note  on  temperature  effects  were  a 
group  of  workers  in  the  latter  half  of  the  nineteenth  century.  The 
most  important  of  whom  were  Merrifield,  V/eismann,  Standfuss,  Fischei 
Edwards  and  Dorfmeister,  All  of  these  workers  studied  the  effect 
of  temperature  upon  Lepidoptera  larvae.  The  experiments  however 
were  carried  on  without  an  attempt  to  control  other  environmental 
conditions.  Tower(l906)  studied  the  effect  of  temperature  upon 
Leptinotarsa  keeping  all  other  conditions  as  constant  as  possible. 
The  results  obtained  were  similar  to  those  obtained  by  earlier 
workers,  namely  that  an  increase  or  decrease  in  temperature  either 


-3- 


acceleratee  or  retards  color  development,  modifying  coloration 

either  toward  albinism  or  melanism.  He  found  that  between  the 

o o 

temperatures  of  16  and  28  there  is  an  increase  to  melanism  and 
above  or  below  these  temperatures  there  is  a decrease  to  albinism. 

In  a few  known  cases  temperature  determines  certain 
characteristics  of  the  animal.  Thus  Baur  found  that  in  Primula 
sinensis  which  under  ordinary  conditions  produces  red  flowers  when 
put  at  a temperature  ranging  from  30°  to  35°  white  flowers  are 
produced.  Miss  Hoge  found  that  in  a race  of  Drosophila,  in  which 
reduplication  of  legs  occured,  under  ordinary  conditions  only  10 % 
of  the  offspring  of  a pure  race  showed  this  condition.  When  the 
eggs  of  these  same  flies  are  subjected  to  a temperature  of  9°  or 
1C°  the  percentage  is  increased  to  almost  100. 

These  experiments  were  not  however  suited  for  a quantita- 
tive analysis  of  temperature  effects.  It  was  van’t  Hoff  who  show- 
ed that  the  speed  of  a chemical  reaction  for  an  interval  of  10°  is 
doubled  or  trebled.  This  is  known  as  the  temperature  coefficient 
or  Q,iq.  It  is  found  by  the  following  formula, 

vt-ao=  Vt^lO 

_ - Vt +10° - 

^10“  - 2 or  3 for  chemical  reactions. 

Vt 

When  a rise  in  temperature  causes  a decrea.se  of  an  action  then 
Q,10  obtained  by  the  use  of  the  following  formula 

vt-ios  MlO 

^io  * 

Vt 

The  quotient  would  thus  become  negative.  In  physical  processes 


-4- 


ql0  has  "been  found  to  he  negative  or  under  2.  In  chemical  reactions 
is  greater  than  2 or  3 for  the  lower  temperatures  and  less 
than  2 for  the  higher.  When  a given  process  follows  the  van’t  Iloff 
law  it  is  an  exponential  function  of  the  temperature  and  when 
plotted  it  is  an  exponential  curve. 

Snyder  and  Arrhenius  formulated  two  equations  which  make 
it  possible  to  compare  the  constants  of  physiological  processes 
with  those  of  chemical  reactions.  Snyder’s  formula  is  a.s  follows, 


*0 


10 

ti-to 


a.  ^ is  the  coefficient  of  increase  in  reaction  velocity  for  a rise 

10 

of  10°  Celsius,  The  symbols  K-,  and  K represent  the  rate  of  the 

1 0 

physiological  processes  at  the  temperatures  t-,  and  tr . 

The  formula  of  Arrhenius  is  as  follows, 


Nat.  Log.  ^ = (lUSl). 

K*  2 T1110 


0 


K and  K represent  the  rates  of  the  physiological  orocesses  at  the 

1 0 

temperatures  T-,  and  . The  symbol  indicates  a constant  value 
which  is  13,500  for  ordinary  chemical  reactions  although  it  varies 
to  some  extent. 

When  the  temperature  of  vital  tissue  is  altered  there  is  a 
change  in  the  physiological  processes.  This  change  can  be  accounted 
for  partly  upon  the  basis  that  the  physiological  processes  are 
chemical  in  nature  and  therefore  follow  the  same  laws  as  chemical 
actions.  The  range  of  temperature  at  which  these  physiological 
processes  are  affected  is  approximately  between  0°  to  42°C.  Hear 


f . i • -■ 


• i r j \ \ . ~ ( fc.i  I 


I V - ■>  ' V V i»V  V.  • : C - . v 


U ! s : , . j 

1 t • r.  • 


i : ^ ( .v  ■.  i-.'j  m •-  > t 5-i 

« * * * . i A t / --  N.  ' - ’t  1 C J I 1 i ^ 


• 1 it  ' . 


^ i 


t".  * i *V.»  - ^ A*  / •*  * ^ \ ‘ 


, ^ i ••  L « . !/•  - %/ 


v*  S • - ♦ « 4 • ’ 1 * * ’•  •*  ■*  J J - ' t • * •*  I 


\ . « * • ^ ^ 


■ V.  ..  • >L<  v J V>«* 


V • - - ‘ - 

. . 


f 


.1- 


„ w*  *.  • » w ?4.  M ^ •» 

...  . o i _ ^ — J ~ 


0°  the  aqueous  solutions  in  the  protoplasm  freeze  and  the  vital 
processes  are  retarded  until  death  takes  place.  Above  40°vital 
processes  also  become  hampered  finally  resulting  in  the  death  of 
the  organism.  There  are  however  no  definite  temperatures  at  which 
death  takes  place,  there  are  only  temperature  zones  in  which  the 
physiological  processes  become  more  and  more  disturbed  finally 
resulting  in  the  death  of  the  animal.  The  manner  in  which  temper- 
ature affects  the  individual  depends  to  a certain  extent  upon  what 
its  past  history  has  been.  Thus  Dallinger  was  successful  in  raising 
Flagellata  at  70°  which  under  ordinary  conditions  died  when  brought 
from  15°  to  23°.  Davenport  experimented  with  tadpoles  and  found 
that  when  they  were  reared  at  15°  went  into  heat  rigor  at  41°  while 
if  raised  at  24°  or  25°  they  died  at  43°. 

The  temperature  coefficients  of  the  physiological  processes 
diminish  from  the  lower  to  the  higher  temperatures  in  the  same 
manner  as  for  chemical  reactions.  The  variations  of  are  however 

greater  for  the  vital  processes  than  for  the  chemical  ones.  This 
variation  as  has  been  suggested  by  workers  is  due  to  the  enzymes 
acting  as  catalytic  agents  thus  affecting  the  speed  of  the  reaction 

The  first  application  of  the  van’t  Hoff  law  for  tem- 
perature effect  upon  living  matter  was  made  by  Cohen.  He  pointed 
out  that  the  output  of  C0o  in  Claussen’s  experiments  with  germinat- 
ing  seeds  of  lupine  and  wheat  and  by  the  blossoms  of  Syringa 
chinensis  followed  the  same  law.  Between  the  range  of  0°  to  25°  an 
increase  of  10°  caused  an  increase  of  2^>  times  the  amount  of  CO.  . 

Among  the  biologists  Oscar  Hertwig  while  working  upon  the 
changes  of  the  rate  of  development  of  frogs  eggs  at  different 


-6- 

temperatures  was  the  first  to  note  that  even  here  chemical  re- 
actions were  affected  by  temperature.  It  was  Cohen  however  who 
Showed  that  the  effect  produced  by  the  temperatures  followed  the 
same  law  as  that  for  chemical  reactions. 

Since  the  year  1905  much  work  has  been  done  upon  the 
application  of  the  van’t  Hoff  rule  to  physiological  processes  in 
general.  It  has  been  applied  to  processes  as  heart  beat,  contrac- 
tion of  the  vacuoles  in  protozoa,  muscular  contraction  and  digest- 
ion. Temperatures  effects  have  also  been  applied  to  rate  of  growth 
and  development. 

Peter  worked  upon  the  Echinoderms  eggs  and  has  shown  that 
the  rate  of  development  follows  the  same  temperature  law.  Snyder 
found  that  the  rate  of  heart  beat  of  the  Pacific  terrapin  is  in- 
fluenced by  the  temperature  changes.  He  found  that  the  minimum 

0 o c 

contraction  occurs  at  0 C and  the  maximum  rate  between  35  and  3V. 5. 

The  temperature  coefficients  varied  to  a considerable  extent  rang- 
ing from  10.2  for  the  temperature  interval  of  0°  to  10°C  and  de- 

o o 

creasing  to  2.2  for  the  interval  of  10  to  20  , 1.9  for  the  in- 
terval of  20°  to  30°, and  finally  falling  to  1 for  the  range  be- 
tween 30°  to  40°C.  He  found  the  same  thing  in  the  mollusc, 
Phyllerrhoe,  and  in  a crustacean.  Kobertsonf 1906 ) found  the  same 
thing  in  Laphnia.  Martin,  Applegarth,  Langendorff  and  Lehmann 
found  that  temperature  effects  were  similar  in  the  hearts  of  dogs, 
cats  and  rabbits  as  the  temperature  effects  described  by  Snyder. 

Rogers(191l)  worked  upon  the  contractions  of  the  dorsal 
blood  vessel  in  Nereis  and  Tubifex  and  the  heart  of  Eundulus.  He 
found  that  these  contractions  were  altered  in  response  to  tempera- 


-7- 

ture.  The  slower  rates  were  always  at  the  lower  temperatures  and 
the  faster  rates  were  at  the  higher.  The  values  of  Q]_q  were  found 
to  he  higher  for  the  lower  temperatures  and  lower  for  the  higher, 
temperatures, 

Riddle(1909)  in  his  work  upon  digestion  in  cold-blooded 
animals  showed  that  this  process  followed  the  same  trend.  He 
attributes  the  increase  of  the  coefficient  of  the  reaction  velocity 
as  the  temperature  0 is  approached  as  due  to  the  destructive  effect 
of  the  temperature  upon  the  digestive  secretions. 

The  temperature  effects  upon  the  pulsation  of  medusae  have 
been  worked  out  by  E.  Veresso  and  Harvey.  The  forms  Cotylorihiza 
and  :>.hizostoma  which  the  former  worker  used  went  into  heat  rigor 
at  24°  or  25°,  as  a result  the  temperatures  were  confined  to  a 
narrow  range.  His  results  are  as  follows: 

Temperature  Pulsations 


14 

17.5 
20 

21.5 


80 

112 

140 

155 


Q10 

2.6 

2.3 


Harvey  working  upon  Cassiopia  obtained  the  following  results, 
Temperature  Pulsations  Q-^q 


16 

20 

25 

30 


8 

17 

26 

33 


6.5 
2.3 

1.6 


The  first  work  on  the  application  of  the  temperature  law 
upon  the  rhythm  of  breathing  was  done  on  different  species  of  fish 
by  Baglionia( 1907 ) . The  work  was  carried  on  in  August  and  the 
beginning  of  December  at  the  Haples  Zoological  Gardens.  The  tem- 
perature of  the  water  at  these  times  was  23°  and  14°  respectively. 


■ 


■ 


-8- 

In  all  cases  the  frequency  was  greater  at  the  higher  temperatures. 
QlO  varied  from  1.8  to  4.5.  The  work  of  this  nature  upon  warm 
blooded  animals  was  carried  on  by  Sciglianos.  The  latter  investi- 
gator subjected  guinea-pigs  to  temperatures  of  39°  and  47°.  At  the 
lower  temperature  the  frequency  of  breathing  was  66  per  minute  and 
at  the  higher  temperature  it  was  144  per  minute.  The  temperature 
coefficient  was  2.7.  He  also  collected  data  of  fever  patients.  The 
Q10  ranged  from  1.8  to  2.8. 

In  1872  Rossback  worked  upon  the  temperature  effect  on  the 
rhythm  of  vacuole  contraction  in  Infusoria.  He  found  that  the 
rhythm  was  constant  at  a given  temperature  but  changed  to  a marked 
degree  at  different  temperatures.  Kanitz  within  recent  years  has 
found  that  the  law  of  temperature  coefficients  also  holds  here. 


This  work  was  carried  on  under  the  direction  of 
Doctor  Charles  ^eleny,  whom  I wish  to  thank  for  his  interest  in 
the  problem  and  for  his  many  valuable  suggestions. 


- 9“ 


II.  Materials  and  Methods. 

The  stock  which  was  obtained  from  Doctor  Zeleny  was  number 
2054.1.  This  number  refers  to  the  stock  which  arose  from  a reverse 
mutation  of  low  selected  bar  80  forked  number  1961.5. 

All  of  the  matings  made  were  mass  matings.  The  flies  were 
raised  on  banana  agar  inoculated  with  yeast. 

Temperature  Control:  The  temperatures  used  ranged  from  15° 
to  31°.  Each  temperature  interval  was  2°.  Constant  temperatures  of 
15°  and  25°  are  maintained  in  the  cold  and  warm  rooms  respectively 
by  forcing  air  over  brine  coils  and  redistributing  it  to  the  rooms. 
Steam  pipes  are  also  present  in  the  warm  room.  The  temperature  of 
27°  is  maintained  in  a Chicago  Surgical  Supply  incubator  in  the  25° 
room.  A similar  incubator  gives  a temperature  of  17°  in  the  15° 
room. 

Aquaria  were  used  to  maintain  temperatures  of  19°, 21°, 23° 
and  31°.  In  these  aquaria  regulators  controlled  the  flow  of  hot  and 
cold  water.  A temperature  of  29°was  obtained  by  the  use  of  a 
Chicago  Electrical  Supply  incubator  in  the  laboratory. 

The  temperature  records  at  17°  and  27°  are  kept  by  a Tycos 
recording  thermometer  while  Tycos  thermographs  keep  the  records  for 
the  15°  and  25°  rooms.  All  records  of  the  aquaria  were  kept  by  the 
Eriez  soil  and  water  thermographs. 

Technique : The  flies  were  etherized  and  then  placed  in  2 to 
3$  caustic  potash  solution  for  a period  of  24  to  36  hourB.  They  were 
then  placed  in  a solution  of  70$  alcohol  for  dissection.  The  cornea 
was  removed  under  a binocular  and  then  placed  on  a slide  and  separat- 
ed into  parts  to  obtain  a flattened  surface.  A coverglass  was  then 


J II  II 


. 


-10- 


placed  over  it.  The  facets  were  counted  under  a Leitz  objective 
number  3 and  a number  4 ocular.  Spider  web  cross  hairs  were  used  to 
mark  off  the  ocular  field  into  parts  to  facilitate  counting. 

Sources  of  Error:  The  chief  sources  of  error  are  1)  those 
due  to  counting  and  2).  variations  in  temperature. 

The  sources  of  error  due  to  countimg  are  of  extreme  import- 
ance here  because  of  the  number  of  facets  to  be  counted.  To  deter- 
mine the  personal  error  of  counting  slides  were  made  and  then 
numbered.  The  first  count  was  then  made,  after  several  hours  or  a 
day  these  same  slides  were  recounted.  Six  corneas  were  recounted  in 
this  manner.  The  difference  in  facet  counts  ranged  from  4 to  16. 

The  following  are  the  first  and  second  counts  made 


1st  counts 

2nd  counts 

695 

703 

716 

720 

630 

621 

745 

740 

672 

683 

650 

634 

Counts  were  also  made  with  a number  7 objective  to  deter- 
mine whether  a marked  difference  would  result  from  a higher 
magnification.  In  these  cases  the  number  of  facets  was  first  counted 
under  a number  3 objective.  The  slides  were  then  put  away  for  a 
time  and  recounted  under  a number  7 objective.  The  difference  in  thq 
counts  were  4,  6,  14.  This  difference  was  therefore  no  greater  than 
the  difference  found  in  the  personal  error. 


-11- 


The  temperatures  of  15° , 17°, 25°  and  27°  were  the  most 
constant.  In  all  four  cases  they  did  not  vary  more  than  -0.5°C.  The 
other  temperatures  varied  to  a greater  extent.  At  19°  while  the 
flies  were  developing  the  temperature  varied  from  18°  to  20°.  The 
21°  aquarium  at  one  time  was  19.8°  and  at  another  22°;  the  31° 
aquarium  varied  from  30°  to  32°.  Since  the  facet  reaction  period 
has  not  been  determined  for  full,  the  assumption  that  it  is  when 
32$  to  45$  of  the  development  has  been  completed  as  for  ultra- "bar 
(Krafka  1920)  may  involve  a considerable  error. 

Method  of  Tabulation:  It  was  at  first  determined  whether 
the  decrease  is  an  exponential  or  a linear  one.  For  this  purpose 
tables  1 and  2 were  made  for  females  and  males  respectively.  In 
these  tables  the  average  observed  facet  counts  at  each  temperature 
are  given,  also  the  calculated  exponential  decrease  of  2.5$,  and 
a linear  decrease  of  2.5$  of  the  mean  at  23°.  In  all  the  calculated 
data  the  mean  facet  value  at  23°  was  used.  The  2.5$  decrease  was 
found  by  finding  the  logarithms  of  the  mean  facet  counts  of  two 
temperatures,  subtracting  then  and  dividing  by  the  temperature 
interval.  The  natural  number  was  then  found  corresponding  to  this 
logarithm.  For  example,  the  mean  facet  number  for  the  females  at  17( 
was  found  to  be  895.1,  at  27°  it  was  found  to  be  698.5.  The  log- 
arithms of  these  numbers  are  2.951872  and  2.844166  respectively. 

Subtracting  these  we  get  0.107706,  dividing  by  the  temperature 

o 

interval  which  is  10  the  logarithm  0.010770  is  obtained  which  is 
the  logarithm  of  1.025.  The  percent  of  change  for  the  interval  is 
thus  2.5$, 


-15- 
Table  2. 


Temperature 
in  °C. 

Observed 

Means 

Calculated  2.5 % 
exponential  de- 
crease. 

Calculated 
2.5$  linear  de 
crease. 

15 

955.9 

941.1 

949.9 

17 

908.5 

895.7 

910.5 

19 

855.2 

852.6 

870.7 

21 

827.6 

851.8 

851.1 

25 

791.5 

791.5 

791.5 

25 

751.1 

752.5 

751.9 

27 

710.1 

715.2 

712.5 

29 

687.7 

679.9 

672.7 

51 

678.5 

646.4 

655.1 

Facet  number  in 

full- eyed  males. 

-14' 

The  last  columns  in  the  tables  represent  a 2.5$  of  the  mean 
o 

at  23  . This  was  found  to  be  39.0  for  the  females  and  39.6  for  the 
males  for  an  interval  of  2°. 

By  the  comparison  of  the  observed  facet  counts  with  those 
which  were  calculated  it  can  be  easily  seen  that  the  exponential 
and  the  linear  decrease  of  2.5$  of  the  mean  at  23°  correspond  to 
a certain  extent  to  the  observed  facet  counts.  Prom  the  irregular- 
ities in  the  facet  counts  obtained  it  was  impossible  to  determine 
with  any  marked  degree  of  certainty  whether  the  decrease  is  an 
exponential  or  a linear  decrease. The  observed  counts  show  however 
one  characteristic  of  the  exponential  decrease,  that  is  that  the 
highest  counts  were  obtained  at  the  lower  temperatures  and  the 
lowest  counts  were  obtained  at  the  higher  temperatures.  Prom  this 
fact  and  also  that  the  decrease  in  the  number  of  facets  of  the  bar 
and  ultra-bar  stocks  has  been  found  to  be  exponential,  the  same 
system  of  tabulation  as  for  these  stocks  was  used. 

Zeleny(1920)  has  shown  that  the  difference  of  the  average 
mean  facet  values  is  not  a good  measure  of  temperature  effect  but 
that  the  change  should  be  expressed  in  units  affecting  the  differ- 
ence in  facet  number.  Upon  this  bases  the  factorial  unit  system  was 
made  for  bar  and  ultra-bar.  This  system  is  based  upon  the  compound 
interest  law.  In  the  particular  case  given  the  mean  facet  values  of 
each  class  represent  & difference  of  10$. 

Upon  this  basis  that  the  decrease  in  full  is  an  exponent- 
ial deorease  of  2.5$,  a system  was  made  on  the  same  order  as  that 
for  the  bar  stocks.  Since  there  was  a slight  difference  between 


-15- 

the  counts  obtained  for  the  females  and  males  at  all  temperatures, 
different  zero  points  were  used.  These  zero  points  were  taken  as 
the  average  of  the  counts  at  25°.  This  average  was  obtained  by 
finding  the  logarithms  of  the  observed  counts  at  that  temperature, 
dividing  by  the  number  of  flies  counted  and  finding  the  natural 
number  of  the  logarithm  thus  obtained*  For  the  females,  the  zero 
point  was  found  to  be  740  and  for  the  males  750*  The  facet  classes 
containing  these  points  would  thus  be  731-749  for  the  females  and 
741-759  for  the  males.  Tables  3 and  4 give  the  distribution  of  the 
counts  in  facet  classes  at  the  different  temperatures  for  females 
and  males  respectively. 


Table  3, 


Classes 

units 

in  2.5$  Classes  in 
facets. 

15 

17 

19 

21 

23 

25 

27 

29 

31 

-7 

606-622 

1 

-6 

623  639 

1 

1 

-5 

640-656 

1 

1 

4 

-4 

657-674 

1 

2 

3 

3 

-3 

675-692 

3 

1 

1 

• 2 

693-711 

1 

2 

1 

-1 

712-730 

1 

2 

2 

1 

0 

731-749 

1 

3 

+ 1 

750-769 

1 

3 

2 

+ 2 

770-789 

2 

2 

1 

- 3 

790-810 

2 

1 

1 

2 

+4 

811-831 

2 

2 

•'5 

832-853 

3 

3 

1 

2 

+6 

854-875 

1 

1 

2 

+7 

876-898 

1 

3 

3 

1 

+8 

899-921 

1 

-'9 

922-945 

3 

1 

*'10 

946-970 

1 

til 

971-995 

3 

0.2 

996-1021 

1 

+13 

1022-1047 

+14 

1048-1074 

1 

Data  of  full  females,  showing  the  distribution  in  olasses 
at  different  temperatures. 


: 


- 

r 


. 

, 

: 


■ 

<■ 


-13- 


III*  Results  of  Experiments. 

The  results  of  the  experiments  are  summarized  in  tables  5 

and  6 for  the  females  and  males  respectively.  In  these  tables  the 

temperatures,  the  number  of  flies  counted  at  these  temperatures, 

the  arithmetical  means,  the  means  in  terms  of  factorial  units  and 

the  differences  for  the  intervals  are  given.  It  can  readily  be 

seen  that  temperature  causes  a decrease  in  facet  number  from  15° 
o 

to  31.  The  differences  between  the  means  are  not  constant.  The 

greater  differences  are  found  between  the  means  of  the  lower 

temperatures  and  the  least  difference  is  produced  at  the  higher 

o o 

temperatures.  Thus  the  interval  of  15  to  17  produces  a change  of 
2.2  factorial  units  for  the  females  and  2.1  factorial  units  for 
the  males.  The  interval  from  29°  to  31°  produces  a change  of  0.9 
factorial  units  for  the  females  and  0.6  factorial  units  for  the 
males. 

Figures  1 and  2 give  the  facets  in  facet  classes  plotted  in 
terms  of  the  temperature. 

Sexual  Dimorphism:  A slight  sexual  difference  was  found  at 
all  temperatures.  The  average  ratio  between  the  mean  facet  number 
of  the  males  and  females  was  found  to  be  0.984. 


_ _ 


. 


. 


9 :'U| 


' 


-20- 


Table  6. 


Temperature 
in  0 C. 

Number  of 
flies  counted. 

Mean  facet 
values. 

Means  in 

factorial 

units. 

Difference 
in  factorial 
units  for 
interval. 

15 

10 

953.9 

+ 9.4 

2.1 

17 

10 

908.3 

7.3 

2.4 

19 

10 

855.2 

+ 4.9 

1.2 

21 

10 

827.6 

+ 3.7 

1.7 

22 

10 

791.5 

+ 2.0 

2.0 

25 

10 

751.1 

0.0 

2.1 

27 

10 

710.1 

-2.1 

1.1 

29 

10 

687.7 

-3.2 

0.6 

3.1 

10 

678.5 

-2.9 

Summary  of  the  effect  of  temperature  upon  full- eyed  males. 


. 


r 


•- 


% 


-25- 


IV,  Discussion, 

The  counts  for  full  at  27°  as  given  "by  Krafka  give  a mean 

facet  value  of  810.6  for  the  females  and  849.9  for  the  males.  His 

counts  at  15°  are  insufficient  in  number  to  give  a mean  facet 

value,  however  2 females  gave  an  average  of  1,084  and  1 male  a 

count  of  1,016.  In  this  experiment  the  counts  obtained  at  27°  were 

o 

6S8.5  for  the  females  and  954.9  for  the  males.  At  15  the  counts 
were  943.3  for  the  females  and  954.9  for  the  males.  The  difference 
in  the  facet  counts  in  the  two  sets  of  data  may  be  due  to  the 
different  stocks  used.  Krafka  used  the  wild  full- eyed  flies  while 
the  ones  used  in  this  experiment  were  mutants.  The  conditions 
under  which  they  were  raised  were  also  different.  Thus  Krafka 
raised  the  wild  fulls  on  a culture  of  fermented  banana  while  the 
stock  in  the  present  experiment  was  raised  on  banana  agar  as 
previously  pointed  out. 

The  range  in  the  counts  is  greater  in  the  wild  flies.  At 
27°  this  range  was  from  632  to  924  for  the  females  and  700  to  980 
for  the  males.  The  same  temperatures  gave  a range  of  653  to  757 
for  the  females  and  662  to  773  for  the  males  in  the  stock  used  in 
the  present  experiment.  This  difference  may  be  explained  upon  the 
basis  that  germinal  diversities  have  been  selected  out. 

Although  temperature  affects  the  facet  number  in  full  the 
change  produoed  is  not  as  great  as  that  of  its  allelomorphs.  Thus 
the  exponential  decrease  for  full  is  2.5$  or  a linear  deorease  of 
39.6  facets  for  the  males  and  39.0  facets  for  the  females.  In  bar 


- 


. 


. 


. - . ...  - 


-24- 


and  ultra-bar  it  is  9.6 $ and  8.7 $ respectively.  The  change  per 

degree  however  shows  one  feature  in  common  in  all  three  cases,  that 

is  that  the  greater  change  occurs  at  the  lower  temperatures  while 

0 

the  least  change  occurs  at  the  temperature  interval  of  29  to  31  • 

Here  the  oounts  show  a very  small  difference  and  the  curves  tend  to 

flatten  out  indicating  that  there  is  a critical  temperature  for 

o 

facet  reaction.  This  critical  temperature  is  27  for  all  stocks. 

The  sex  coefficients  for  the  bar  stocks  as  determined 
by  Krafka  is  0.791  while  for  full  it  is  0.984.  Zeleny(1920)  has 
shown  that  the  probable  cause  of  sex  dimorphism  in  the  bar  stocks 
is  due  to  accessory  factors.  Since  these  seem  to  be  sex-linked  the 
stock  would  consist  of  heterozygous  females.  The  result  of  selection 
for  facet  number  would  cause  a decrease  in  the  heterozygous  factors. 
The  greater  this  decrease  would  become  the  closer  the  sex  coeffic- 
ient would  approach  unity.  If  it  wo\ild  be  unity  the  counts  of  the 
males  and  females  would  be  the  same.  The  close  approach  of  the  sex 
coefficient  of  full  to  unity  may  thus  be  explained  upon  the  basis 
that  there  has  been  a decrease  in  accessory  factors  due  to  select- 
ion. 


, 


. 


< I 


-25- 


V.  Summary. 

1.  Temperature  causes  a decrease  in  facet  number  in  the 
full-eyed  race  between  the  experimental  temperatures  of  15°  to  31°. 

2.  It  can  not  be  definitely  determined  from  the  counts 
whether  the  decrease  is  of  an  exponential  or  linear  order.  The  fact 
that  the  effect  is  greater  at  the  lower  and  least  at  the  higher 
temperatures  seems  to  indicate  that  it  is  an  exponential  decrease. 

3.  The  temperature  effect  in  full  is  not  as  marked  as 
the  temperature  effects  on  the  bar  stocks.  In  full  the  effect  is 
approximately  a 2.5  % exponential  decrease  while  in  bar  it  is  9.5% 
and  in  ultra-bar  it  is  8.7%. 

4.  The  critical  temperature  for  change  in  facet  number 
is  at  27°  as  in  all  bar  stocks. 

5.  The  sex  dimorphism  in  the  full- eyed  race  is  0.984 
while  in  the  bar  stocks  it  is  0.791. 


-26- 


Bibliography. 

Hoge,  M.  A.  1915.  The  Influence  of  Temperature  on  the  develop- 
ment of  a Mendelian  Character.  Journ.  Exp.  Zool.,  18:241- 
286. 

Aanitz,  Aristides  1915.  Temperatur  und  Lebensvorgange. 

Krafka,  Joseph  1920.  The  Effect  of  Temperature  upon  Facet 

Number  in  the  Bar-eyed  Mutant  of  Drosophila.  Journ.  Gen. 
Phys.,  2:409-464. 

Rogers,  Charles  1911.  Studies  upon  the  Temperature  coefficient 
of  the  Pate  of  Heart  Beat  in  certain  Living  Animals. 

Amer.  Journ.  Phys.  28:81-93. 

Seyster,  E.  W. , 1919.  Eye  Facet  dumber  as  Influenced  by 

Temperature  in  the  Bar- eyed  Mutant  of  Drosophila  melano- 
gasterf ampelophila) . Biol.  Bull.,  37:168-181. 

Snyder,  Charles  1906.  The  Influence  of  Temperature  upon  the 
Hate  of  Heart  Beat  in  the  night  of  the  Law  for  Chemical 
Reactions.  Amer.  Journ.  Phys.  17:350-361. 

1911.  On  the  Meaning  of  Variation  in  the 
Magnitude  of  Temperature  Coefficients  of  Physiological 
Processes.  Amer.  Journ.  Phys.  28J167-175. 

Zeleny,  Charles  1917.  Germinal  Changes  in  the  Bar- eyed  Race 
of  Drosophila  during  the  Course  of  Selection  for  Facet 
Humber.  Proc.  Ind.  Acad.  Sci.,  73-77. 


-27- 


1920,  The  Tabulation  of  Factorial  Values, 
Amer,  Nat.,  54:358-376, 

1920.  A Change  in  the  Dar  Gene  of  Drosophila 
melanogaster  Involving  further  Decrease  in  Facet  Humber 
and  Increase  in  Dominance.  Journ.  Exp.  Zool.,  30:293-324. 

1921.  Decrease  in  Sexual  Dimorphism  of  Bar 
Eye  during  the  Course  of  Selection  for  Low  and  High  Facet 
Dumber.  Amer.  Nat.,  55:404-411. 


